Bandwidth signalling

ABSTRACT

The invention relates to bandwidth signalling in a multicarrier wireless telecommunication system. The information is transferred in the band itself (bold carriers) and contains information of the size and location of the band (I). The information is repeated in a number of carriers (bold) throughout the band.

RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 14/556,871 filed Dec. 1, 2014, which is a continuation of U.S.patent application Ser. No. 10/596,859, filed Jun. 27, 2006, nowabandoned, which is the National Stage of International Application No.PCT/SE2004/02045, filed Dec. 29, 2004, which claims the benefit ofSwedish Application No. 0303607-6, filed Dec. 30, 2003, the disclosuresof which are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to signalling of available bandwidthespecially in multicarrier wireless telecommunication systems.

BACKGROUND

A tendency of new wireless telecommunication systems is that they oftenrequire more bandwidth than existing systems, as new and more demandingservices are likely to be introduced by the new systems. However, theavailable spectrum is limited and it is difficult to identify newspectrum for new communication systems, especially if the new spectrumshall be identical in all different regions of the world. This calls fora need of flexibility with respect to spectrum usage in the sense thatpieces of radio spectrum of different size and in different frequencybands should be used with basically the same radio air interface.

For the sake of example, assume that the most demanding applicationsrequire that the system bandwidth needs to be 100 MHz. Internationalstandardisation and regulatory bodies will therefore have to make surethat there will be ample spectrum available so that a number of 100 MHzbands could be offered to the customers. However, it is also likely thatcertain regions will have smaller pieces of spectrum available here andthere that are smaller than 100 MHz, say a 30 MHz band in one region anda 66 MHz band in another.

One possibility is to design many different air interfaces for a numberof bandwidths—say 30, 66 and 100 MHz—and let the base stations andmobile users choose one or several of them depending on the situation,say a 25 MHz air interface for the 30 MHz band, a 50 MHz interface forthe 66 MHz band and 100 MHz interface for the 100 MHz band. This howeverleaves some parts of the spectrum unused: 5 MHz in the 30 MHz band and16 MHz in the 66 MHz band, while the 100 MHz band is fully used. Even ifthere is a high degree of commonality between different air interfaces,the complexity of equipment with several air interfaces will besignificantly larger than if only one air interface can be used instead.

Another suggestion for better usage of available frequency spectrum isto let several operators share spectrum or rent or buy resources fromeach other.

SUMMARY OF THE INVENTION

The proposals and ideas referred to above suffers from a number ofdrawbacks. Already mentioned is that using different air interfaces inseveral parts of the spectrum causes greater complexity. Another is thatavailable pieces of spectrum might be too big for certain applications,which leads to a waste of resources. Still another problem is how toinform the users of the existence and extent of free spectrum for acertain application at a certain moment in a certain location area. Inother words there is a need for greater flexibility and fast allocationof resources whenever the users so request.

The solution is presented in the appended claims relating to a methodand means for signalling the availability of spectrum in terms ofbandwidth and location.

The invention is advantageously implemented in wireless multicarriersystem where the total maximum bandwidth is made up of a large number ofnarrowband sub carriers like for example in Orthogonal FrequencyDivisional Multiplexing, OFDM, Interleaved Frequency DivisionalMultiplex, IFDM or similar. In OFDM and IFDM the sub carriers areideally mutually orthogonal. Generally, very similar systems can bedesigned with pulse shapes that make the sub carriers slightlynon-orthogonal but that have other good properties, for example betterspectral properties. This difference does not have a bearing on theinvention so when OFDM is mentioned in the examples below, also theseother more general types of systems are applicable. The only thing thatis important is that the system consists of a large number of subcarriers.

With a multicarrier system it is easy to adjust the used systembandwidth by simply switching off some blocks of sub carriers. However,a problem with this solution is how to inform the mobiles about the sizeand location of the spectrum that is currently used by the communicationsystem. The invention described here solves this problem by includingthis size and location information within the sub carriers blocksthemselves.

The information about which set of downlink carriers in a block that isavailable is sent downlink from the base station on an acquisitionchannel, a broadcasting channel or some other cell covering channel. Atleast one easily detected downlink channel must be transmitted which iswithin an operational band known to the mobile user and containsinformation about where this operational band starts and stops relativeto the location of said downlink channel. It is enough if the user has arough idea of where the operational band can be found. This kind ofrough information could have been broadcasted to the user in an earliercell search.

The format of the information about the size and location of theoperational band could vary. Here are some examples:

-   -   A start and stop frequency or frequency number is given        absolutely or relative to the location of the channel containing        this information.    -   A start frequency or frequency number is given, absolutely or        relatively specified, plus a number of maximum carriers or a        fraction of that number.    -   An identifying number where said identifying number identifies        an operational bandwidth from a list of predefined operational        bandwidths.    -   The information about the location in spectrum could be        explicitly signalled or implicitly derived by synchronisation        signals.    -   As soon as the mobile is informed of the available resources it        may access a suitable channel representing its needs in the        normal way well known to a person skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further aspects and advantages isexemplified by reference to a number of embodiments and accompanyingdrawings wherein:

FIG. 1 shows a frequency spectrum exemplifying bands available in atypical situation.

FIG. 2 is an overview of the system according to the invention.

FIG. 3 is a flow chart showing the steps of the invention in a furtherembodiment.

DETAILED DESCRIPTION

In FIG. 1 a typical spectrum is shown, divided into three blocks oroperational bands, I, II and III of 100 MHz, the maximal systembandwidth in this example. The spectrum is partly shared by twooperators A and B. A has part I and B has part III while part II isshared between the both operators. It is assumed that, by negotiationbetween the operators, the border b between A and B is changed from timeto time depending on the demand from the subscribers of A and Brespectively. The sharing distribution could of course be different.FIG. 1 is just an example.

N is the number of sub carriers in each part. Lets assume that the 100MHz band is divided into 4096 sub carriers of about 25 kHz each, (i.e.N=4096). In theory any number N could be activated making a large numberof air interface bandwidths possible using just one air interface. Thisis a basic property of these types of systems. An operator can, atdifferent moments, have say 1000, 2000 or 4000 carriers to its disposal,varying with the demands and behaviours of the subscribers.

Assume that the mobile user knows or can guess the approximate locationof all N carriers. First the mobile user must detect the presence of oneor more acquisition channel(s) for cell search purposes. Such channelsare designed so that there is a very small probability to mistake themfor other types of signals, or for other types of signals to be mistakenfor acquisition signals. In general the user must scan all possiblelocations to find this signal in order to unambiguously find one. Thenthe mobile knows that this channel lies within the operationalbandwidth. After that, the information in this acquisition channel aboutthe size and location of the actual carrier set is read.

As an example, the acquisition channel is represented by one or more ofthe bold marked carriers of block I in FIG. 1. Then the information onthe acquisition channel tells the user that the band starts at f1 andstops at f2 and that the bandwidth is f2−f1.

Alternatively, based on acquisition channel information, the mobilefinds another channel that broadcasts control of the system, and readsthe bandwidth information there or part could be read from anacquisition channel and part from another channel that transmitsbroadcast control information.

The system information bold marked carriers are spread out among allpossible sub bands of the operational band. Operator A's signalling isas follows: in the three bold sub carriers to the left in block I,information says that the bandwidth is 100 MHz and all sub bands areused i.e. the whole 100 MHz band, the next three defines a bandwidth ofabout 70 MHz in block II. Operator B's signalling is as follows: Thesingle bold sub carrier defines a ca 30 MHz system bandwidth in blockII, and the next three in block III define a full 100 MHz bandwidth.

Included in FIG. 1 is a piece of unused spectrum in block II thatcomprises a few sub carriers that act as a guard band between the twogenerally unsynchronised and uncoordinated operators. This is sometimesbeneficial in order to reduce the disturbances between the transmittedsignals belonging to the two neighbouring sub bands.

If the operators, in some real time resource exchange or the like,decide that all bandwidth in the second block II should go to operatorA, then operator B simply gracefully finalises or reallocates trafficfrom the allotted carriers in this block, signals that the resource inblock II is closed for random access attempts, and stops transmitting inthis band, while operator A starts to signal that the entire 100 MHzblock is now available for its subscribers.

Since the terminals periodically read bandwidth information from thedownlink control channels, this process could be made very quickly, inthe order of milliseconds. Also, the terminals have or could have a fullbandwidth detector running which makes it trivial to quickly start (de-)multiplexing data (from) to the newly available sub carriers.

In FIG. 1 the bandwidth information is repeated in every forth carrierfor illustrative purposes as mentioned above. In practice, however, thedistribution is much more thinly spread out in order not to wastebandwidth. In a 4096 carrier band the information may be carried onevery 128th or 256th carrier occupying less than one percent of thetotal bandwidth.

In FIG. 2 an overview of the system according to the invention is shown.A traffic control centre, TCC, is connected over suitable interfaces toa number of base station transceivers BS, only one shown in the figure.The base stations have connections with several mobile stations, MS1 andMS2. The TCC has an over all control of the traffic in the system andone of its tasks is to collect information about the availability ofbandwidth of particular parts of radio spectrum used in the system. Theinformation is transferred to the base stations and from theretransmitted on a broadcast channel or the like to the users, MS. The TCCis connected to public networks like the Internet. The TCC may also haveconnections with other TCCs belonging to other operators and afternegotiations taking over smaller or greater parts of spectrum from eachother.

A user, MS1 in FIG. 2 for example, entering the location area of thesystem scans the broadcast channel(s) sent out by the base station forinformation about available bandwidth and location in the spectrumaccording to the invention. MS1, having received the information inreceiver R, stores it into a memory M. After entering the scanning isrepeatedly performed for changing conditions and the memory is updated.

The invention solves the problem of the need for the mobiles to haveknowledge of available bandwidth. The knowledge is collected from asearch of the radio environment for the available resources by detectingsystem information stored in certain sub carriers in the multicarrieroperational bands.

In FIG. 3, a method for downloading information using the invention isillustrated as a number of steps. In step I, a mobile station, MS, has aneed for a multicarrier band with N carriers for the downloading. The MSsearches the radio interface in step II.

The search is simplified by the fact that information about the size andlocation of available bands are stored at specified locations throughoutthe bands e. g. every 128^(th) carrier. The efficiency of the searchcould be even more enhanced if location and size of suitable bands areprestored in the memory M of the MS. In step III an N+ε carrier band isassigned to the MS. ε is a small number or zero. MS downloads theinformation in step IV and thereafter the band could be freed for otherusers, step V.

To conclude the invention has the following advantages:

-   -   The base station uses basically the same signalling method for        any operational bandwidth.    -   The mobiles use basically the same detection method for any        operational bandwidth.    -   The mobile user can use the same detector in OFDM-like systems        regardless of the bandwidth used in a specific cell at a        specific time    -   The mobile user can quickly detect changes in spectrum        allocations.    -   The invention gives regulators (national or international)        flexibility to allocate different sized spectrum pieces for use        with basically the same equipment.    -   The invention gives operators the technical means to trade        spectrum in real time.    -   Furthermore, when regulatory conditions change the operational        bandwidth can be changed quickly with the mobile station still        being able to follow what is happening.

1. A method in a multicarrier wireless telecommunication system forinterchanging radio communication between base stations (BS) and mobileuser stations of the system, the method comprising: receiving, by themobile user station, information signals over a radio interface, theinformation signals relating to a location of one or more operationalbands of a radio spectrum, wherein the received information signalscomprise information of the location in the radio spectrum of the one ormore operational bands as part of the information in one or several subcarriers of the bands, and wherein the received information signalsfurther comprise information relating to a size of the one or moreoperational bands of the radio spectrum, whereby the size is signaled asa bandwidth of the one or more operational bands; searching, by themobile user station, the radio interface for an N-carrier band bylooking for the location and the size information; and downloading, bythe mobile station, information via the N-carrier band.
 2. The method ofclaim 1, wherein the received information signals are received by themobile user stations, which detect information about available blocks ofthe radio spectrum and store the information into a memory.
 3. Themethod of claim 2, wherein the mobile user stations repeatedly scan thereceived information signals for updating memory of the mobile userstations about changing conditions relating to the one or moreoperational bands.
 4. The method of claim 1, wherein the informationsignals relating to size are repeated regularly in subsequent carriersor subcarriers of the one or more operational bands.
 5. The method ofclaim 1, wherein the information of the bandwidth comprises start andstop frequencies of the one or more operational bands and thereby thebandwidth.
 6. The method of claim 1, wherein the information signalscomprise an identifying number representing the size and the location ofthe one or more available operational bands.
 7. The method of claim 1,wherein the operational bands belong to different operators and whereinsubscribers of an operator may partly or wholly have access to one ormore operational bands of another operator.
 8. A method performed by amobile user station, the method comprising: receiving informationsignals over a radio interface, the information signals relating to alocation of one or more operational bands of a radio spectrum, whereinthe received information signals comprise information of the location inthe radio spectrum of the one or more operational bands as part of theinformation in one or several sub carriers of the bands, and wherein thereceived information signals further comprise information relating to asize of the one or more operational bands of the radio spectrum, wherebythe size is signaled as a bandwidth of the one or more operationalbands; searching the radio interface for an N-carrier band by lookingfor the location and the size information; and downloading informationvia the N-carrier band.
 9. The method of claim 8, wherein the receivedinformation signals are received by the mobile user stations, whichdetect information about available blocks of the radio spectrum andstore the information into a memory.
 10. The method of claim 9, furthercomprising: scanning the received information signals for updatingmemory of the mobile user station about changing conditions relating tothe one or more operational bands.
 11. The method of claim 8, whereinthe information signals relating to size are repeated regularly insubsequent carriers or subcarriers of the one or more operational bands.12. The method of claim 8, wherein the information of the bandwidthcomprises start and stop frequencies of the one or more operationalbands and thereby the bandwidth.
 13. The method of claim 8, wherein theinformation signals comprise an identifying number representing the sizeand the location of the one or more available operational bands.
 14. Themethod of claim 8, wherein the operational bands belong to differentoperators and wherein subscribers of an operator may partly or whollyhave access to one or more operational bands of another operator.
 15. Amobile station node for a multicarrier telecommunication system, themobile station node comprising: a receiver; a memory; and processingcircuitry configured to execute program instructions stored in thememory to perform operations comprising: receiving information signalsover a radio interface, the information signals relating to a locationof one or more operational bands of a radio spectrum, wherein thereceived information signals comprise information of the location in theradio spectrum of the one or more operational bands as part of theinformation in one or several sub carriers of the bands, and wherein thereceived information signals further comprise information relating to asize of the one or more operational bands of the radio spectrum, wherebythe size is signaled as a bandwidth of the one or more operationalbands; searching the radio interface for an N-carrier band by lookingfor the location and the size information; and downloading informationvia the N-carrier band.
 16. The mobile station node of claim 15, whereinthe received information signals are received by the mobile stationnode, which detects information about available blocks of the radiospectrum and store the information into a memory.
 17. The mobile stationnode of claim 16, the operations further comprising: repeatedly scanningthe received information signals for updating memory of the mobilestation node about changing conditions relating to the one or moreoperational bands.
 18. The mobile station node of claim 15, wherein theinformation signals relating to size are repeated regularly insubsequent carriers or subcarriers of the one or more operational bands.19. The mobile station node of claim 15, wherein the information of thebandwidth comprises start and stop frequencies of the one or moreoperational bands and thereby the bandwidth.
 20. The mobile station nodeof claim 15, wherein the information signals comprise an identifyingnumber representing the size and the location of the one or moreavailable operational bands.